And it's often treatable through diet and vigorous exercise.
"A weight loss of ~15 kg, achieved by calorie restriction as part of an intensive management programme, can lead to remission of T2DM in ~80% of patients with obesity and T2DM." [ https://pubmed.ncbi.nlm.nih.gov/32690918/ ]
"A novel HIIT-protocol recruiting lower and upper body muscles efficiently improves insulin sensitivity, VO2max and body composition with intact responses in obesity and type 2 diabetes. " [ https://pubmed.ncbi.nlm.nih.gov/36387850/ ]
The caveat, is of course, "long-term weight loss maintenance is challenging."
Type 1 diabetes has nothing to do with diet it is an autoimmune disease with genetic and possible environmental antecedents.
If you're interested in learning more about type 1 diabetes please check out:
https://www.jdrf.org/t1d-resources/about/facts